Historically, there have been two principal methods of making yeast leavened products in the baking industry, namely the "straight dough" method and the "sponge dough" method. Both methods require lengthy periods of fermentation to achieve the desired results in the finished products. In the straight dough method, all of the ingredients of the formula are mixed together to full development. Then the dough must be allowed to stand (ferment) at between about 80.degree. and 86.degree. F. for about 11/2 to 3 hours. Then, after dividing into individual pieces, rounding, and another fermentation period of about 15 to about 25 minutes, commonly referred to as intermediate proof, the dough is molded to the desired shape. The dough then goes through another fermentation period generally of from about 50 to about 90 minutes at between about 100.degree. and 105.degree. F. at a relative humidity of between about 90% and 95%. This fermentation period is commonly known as proofing. During this time, the dough rises to the desired shape and height before going into the oven. After proofing, the dough is baked for between about 18 and 30 minutes at between about 375.degree. and 450.degree. F.
In the commercially more acceptable sponge dough method, from about 50% to about 70% of the flour is mixed with the yeast, yeast nutrient or food, shortening, part of the salt, and an equivalent amount of water to form a stiff dough with little development. This is referred to as the "sponge." Then the sponge is fermented over a widely varying time period, depending on production methods, the time generally ranging from between about 21/2 and 5 hours at a temperature of from about 78.degree. to 80.degree. F. Then the sponge is remixed with the remaining 30% to 50% of the flour and other ingredients, for about 10 minutes or until full development. The dough is then allowed to "relax" for between about 15 and 30 minutes before dividing. From this point the dough is processed as in the straight dough method.
In addition to the foregoing methods, other methods have been developed in recent years to impart the desired characteristics to the finished product. One utilizes a liquid preferment brew. In lieu of a fermented sponge, a liquid brew is prepared, containing some of the dough ingredients, such as part of the yeast, the yeast nutrient, sugar and most of the water. The brew is allowed to ferment for between 30 minutes and 11/2 hours at a temperature of between about 75.degree. and 85.degree. F., after which the brew is chilled and held at about 40.degree. F. until needed. Then a properly measured portion of the brew is added to the remainder of the dough ingredients for each batch, and the dough is mixed to full development. After a short time (between about 1 and 20 minutes, depending upon the particular product being made), machining and proofing operations are carried out as in the straight dough method.
In all of these methods, the fermentation step accounts for up to about 90% of the time involved in a baking process. Fermentation is the step the baker relies upon most to impart to the finished product many of the qualities that are desired.
In order to insure adequate activity of yeast in the dough, and thereby achieve successful fermentation in the bread making process, the baking industry has used successfully through the years various compounds as yeast nutrients or foods. It has long been recognized that, for adequate fermentation, yeast requires more than the sugar normally included in the recipe and the sugar obtained from starch conversion by enzymatic action. Further requirements of yeast include certain mineral salts and nitrogen. A readily accessible source of nitrogen is needed for the active fermentation of sugars to carbon dioxide and alcohol or to carbon dioxide and water.
The compounds that have been used in the past to provide these nutrients in the baking industry have included inorganic salts, namely the ammonium salts of acid radicals such as ammonium sulfate, ammonium chloride, monoammonium phosphate, and diammonium phosphate.
It is common practice in the baking industry to employ as additives so-called "yeast foods" or nutrients. Technically, any substance necessary to support the growth activities of yeast might be classified as a yeast food. In a more limited sense, and as used in this disclosure, unless otherwise noted, the term "yeast food" refers to a combination of yeast nutrients and dough conditioning ingredients. In a typical yeast food of the prior art, a salt usually serves the specific function of a yeast nutrient. Generally, this is an ammonium salt, such as ammonium sulfate, ammonium chloride, or ammonium phosphate. The salt dissociates in solution to yield ammonium ions which are utilized by yeast as a source of nitrogen. The primary function of the yeast nutrient is as a nitrogen source. Although the sulfate and phosphate ions also stimulate yeast activity, dough normally contains adequate amounts of these minerals for yeast activity.
Most other compounds often included in yeast foods fall into three categories. (1) Flour protein (dough) conditioners that contain oxygen or liberate oxygen when added to a dough mass. Typically, the dough conditioners are inorganic salts. Dough conditioners include potassium bromate, calcium bromate, potassium iodate, calcium iodate, azodicarbonamide, ascorbic acid, calcium dioxide, and in some cases various enzymes. (2) Bulking agents are often required due to the reactivity of the ammonium salts with some of the oxidants. The most commonly used oxidant, potassium bromate, requires that the yeast food blend be bulked in order to keep the oxidant separate from the ammonium salt. (3) Water conditioners which consist of chemical salts for water conditioning. Due to a great improvement in the uniformity of municipal water supplies over the years, it is very seldom necessary to add the various chemical salts for water conditioning. Most of these compounds have become bulking agents or carriers for the ammonium salts and oxidizers.